Research On UASB Anaerobic Reactor Cometabolism Degradation Of Aniline Wastewater

Aniline is widely used in various industries as the raw material for many products.With the increase of aniline consumption,aniline-containing substances in the water environment are also increasing,causing water pollution and affecting the ecological balance seriously.Anaerobic biological treatment has the advantages of low operating cost,high degradation efficiency and clean energy generation.The anaerobic co-metabolic biological treatment technology as a new method to deal with refractory toxic and harmful pollutants has been widely concerned by domestic and foreign scholars.However,there are few studies on the mechanism of aniline wastewater degradation by anaerobic co-metabolic biological treatment.As an efficient anaerobic reactor,UASB anaerobic bioreactor has an excellent ability to remove high concentration of organic matter.Therefore,in this paper,UASB anaerobic bioreactor was used to inoculate and treat anaerobic granular sludge from citric acid wastewater,and starch was used as co-metabolizing substrate to degrade aniline.By optimizing the organic load of aniline and starch,the variation rules of COD,aniline content,sludge size and methane-producing activity(SMA)were studied.The change law of dissolved organic matter(DOM)in effluent was studied by PARAFAC and FRI.The microbial community structure at different stages of reactor operation was analyzed by high-throughput sequencing technique.This study provides theoretical basis and technical reference for the practical application of UASB anaerobic reactor in the treatment of aniline wastewater and the mechanism of co-metabolism treatment of aniline wastewater.The main conclusions are as follows:(1)During the start-up of the UASB anaerobic reactor,the content of inlet starch gradually increased from 1.2 gCODL-1d-1 to 7.2 gCODL-1d-1.Under the condition of nitrogen starvation,the COD removal rate was maintained at about 85%,while after the nitrogen source was supplemented,the COD removal rate of the effluent increased to 95%,and the effluent ammonia nitrogen decreased rapidly,indicating that the nitrogen content was the main limiting factor for anaerobic digestion in the nitrogen starvation environment.Through PARAFAC analysis,the main groups of effluent DOM were found to be protein-like,tryptophan and humus-like.The average particle size of sludge increased from 29.7?m to 236.29?m,and the average particle size increased by 7.95 times.The maximum specific methanogenesis rates of hydrogen-trophic methanogens and acetic acid-trophic methanogens were 1.36 times and 2.83 times higher,respectively.(2)The optimal concentration of aniline and starch in the UASB anaerobic reactor was 2.45 gCODL-1d-1 of aniline and gCODL-1d-1 of starch.At this time,the COD removal rate was over 75%and the aniline removal rate was over 81%.FRI analysis revealed that the main group of effluent DOM was divided into protein-like compounds.(3)On the level of phylum classification,in the start-up process,the dominant phylum of bacteria were Bacteroidetes?Chloroflex?Firmicutes?Synergistetes and Therm-otogae with the relative abundance of 21.9%,21.2%,15.3%,8.8%and 6.6%respectively.When aniline concentration was 3.0 gCODL-1d-1,the relative abundance of Bacteroidetes?Proteobacteria?Thermotogae and Actinobacteria increased by 40.3%,54.4%,65.0%and 52.4%respectively,and Spirochaetes?Patescibacteria and Calditri-chaeota appeared.When the concentration of aniline increased to 6.0 gCODL-1d-1,the relative abundance of Bacteroidetes and Firmicutes decreased by 37.8%and 18.6%respectively,while the relative abundance of Chloroflexi and Synergistetes reached the maximum value of 21.6%and 10.2%respectively.(4)At the level of genus classification,the dominant genera were Longilinea?Christ-ensenellacea?Aminivibrio and Bacteroides,with relative abundance of 30.8%,9.3%,8.97%and 8.39%,respectively.When the concentration of aniline was 3.0 gCODL-1d-1,the abundance of Longilinea decreased significantly and the relative abundance was only 0.91%,while Syner?Christensenellaceae and Anaerolinea became dominant genera with relative abundance of 5.5%,15.7%and 5.4%,respectively.Meanwhile,Acinetobacter?Pseudomonas and Paenibacillus with metabolic function of aniline were found in the reactor.When the concentration of aniline load increase to 6.0 gCODL-1d-1,WCHB1-02_Unclassified?Ambiguous_taxa_Unclassified and Spiroch-aetaceae_Unclassified relative abundance increased by 24.5%,13.5%and 26.8%respectively.(5)During the start-up process,methanogens were mainly Methanosaeta,an acetic acid nutrition-type methanogen.When aniline was added for co-metabolism,the abundance of Methanolinea,Methanospirillum,Methanocorpusculum and Methano-bacterium significantly increased.At aniline concentration of 3.0 gCODL-1d-1,the proportion of hydrotrophic methanogens in methanogens increased from 8.3%to 49.5%.When the concentration of aniline increased to 6.0 gCODL-1d-1,the proportion of hydrotrophic methanogens in methanogens increased to 59.7%.